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takyon writes:

Scientists have created an atomic-scale radio receiver using a diamond crystal and a laser:

Physicists at Harvard have built a radio receiver out of building blocks the size of two atoms. It is, almost certainly, the tiniest radio receiver in the world. [...] The researchers replace some of those carbon atoms with nitrogen atoms, and leave a hole next to each one. That nitrogen atom/hole pair, called a nitrogen-vacancy center, basically creates the first two parts of the radio: the power source and the receiver.

A green laser pointed at the nitrogen-vacancy center excites the electrons in the diamond. That's the power. When a radio wave hits those excited electrons around the nitrogen-vacancy center, it's converted into red light. That's the receiver. It's also one of the reasons nitrogen-vacancy centers are so compelling as a building block for tiny machines -- they are natural light emitters. An electromagnet near the receiver can change the frequency to which the receiver is sensitive. That's the tuner. But at that point, your "radio" is just a glowing red light. It still hasn't made any sounds.

For the last step, a common device called a photodiode converts the red light back to an electrical current, and a speaker or pair of headphones grabs that current and broadcasts it as sound.

Also at Harvard.

Diamond Radio Receiver: Nitrogen-Vacancy Centers as Fluorescent Transducers of Microwave Signals (DOI: 10.1103/PhysRevApplied.6.064008) (DX)

Original Submission